Don’t Discount (Smart) Fish Farming

Paul Greenberg is the author of "Four Fish" and a fellow with the Blue Ocean Institute. He is currently writing “The Fish Next Door,” a book about reviving local American seafood.

Updated July 21, 2015, 12:50 PM

Whenever I lecture on sustainable seafood, I usually start off by asking audiences:

“Who here refuses to eat farmed seafood?”

Usually about three-quarters of the hands in the crowd go up in a sanctimonious “Nay!”

This happens despite the fact that half of the world’s seafood is farmed. The negative rap aquaculture gets results from consumers’ inability to distinguish between good and bad farming practices and a failure to examine what makes a creature truly fit for the farm.

If we radically ramped up the farming of bivalves I believe we would be doing the world a great service.

In the good category are farmed clams, mussels and oysters. They require no outside feed, and they clean our waterways as they gobble up micro algae and create habitat for other wild fish. If we radically ramped up the farming of bivalves, we would be doing the world a great service.

Of course, many people don’t want clams all the time, and that’s where aquaculture gets tricky. The growing of popular predatory fish like salmon and tuna, for example, can require many pounds of wild fish as feed, in addition to aquaculture net pens, which are hung in the open ocean. These pens are then stocked densely with farmed fish that can soil the benthic habitat.

But I believe these problems can be fixed. A whole new range of feeds are being developed, so that rather than grinding up wild fish, aquaculturists can make use of waste products like brewery effluent. And increasingly, scientists are figuring out how to grow fish in tanks where they do not interact with or pollute the open ocean.

Nevertheless, even if we fix these problems, we’ll still have to choose our farmed species wisely. Raising high-energy, warm-blooded predators that can swim 40 miles an hour, like the bluefin tuna, just doesn’t feel right for a global population headed toward nine billion people. More docile and fast-growing tilapia and barramundi and air breathing weirdos like the Vietnamese pangasius catfish seem much better adapted to a hot and crowded planet.